Conventional vehicle frames have a pair of rails running longitudinally of the vehicle. The rails not only serve as a structural base around which a vehicle is built, but also serve as a mechanism for absorbing an externally applied intrusive load. Intrusion energy management plays a major role in the design of an automotive vehicle. The goal of many vehicle designers is to have the vehicle absorb the total amount of kinetic energy resulting from the application of such a load. Conventional rail designs have a number of aspects in common to serve this end. The forward rail portion extending from the front of the engine block to the bumper is designed to axially crumple in accordion like fashion. The remaining energy is then typically absorbed by the rear rail portion, extending the length of the engine block, by means of plastic bending deformation. Generally the rail folds upward at the point of greatest eccentricity from the applied load. This point is typically beneath the toe pan area of the passenger compartment.
The toe pan area is rigidly attached to the rails of an automobile. This area typically rides up the lower or rear portion of the rail and separates from the rail at the midpoint just before transitioning into the forward or upper rail. The plastic bending deformation of the rear rail, in conventional designs, occurs at the base of the curve of the rear rail or just beneath a vehicle driver position. When this bending deformation occurs the rail is displaced upward and intrudes into the toe pan area of the passenger compartment.
One approach to avoid this intrusion is to increase the structural rigidity of the rear rail section. With this enhanced rigidity, the rear rail section resists deforming altogether. The advantage with this design being that the rear rail does not deflect upward into the toe pan area upon application of intrusive energy. However, because the rail will not deflect and absorb the remaining energy, the rail acts to transmit the remaining energy to other portions of the vehicle which affects their design.
Accordingly, it is seen that a need exists in the art for a vehicle intrusion energy management frame element which absorbs the kinetic energy resulting from an external load and prevents the intrusion of the rail members into the toe pan area.